Picture of a disassembled Duracell 9v battery. Below the terminal assembly is a clear plastic case where you can see six sets of stacked rectangular terminals and fillings.
I had an old 12v power tool battery die, so I took it apart to find 8 generic AA rechargeables wired together. I suspect lots of batteries are multiples of 1.5v (9/12/18) because they’re just stacked smaller cells that are already mass produced.
Battery chemistry produces fixed voltages depending on what you use. It depends on where the active components sit on the electronegativity table.
The typical ones are:
Zinc-carbon and alkaline - 1.5 volts per cell.
Lead acid - 2 volts
Nickel Cadmium - 1.2 volts
Nickel Metal Hydride - 1.4 ish.
All the Lithium ion combos - 3.4 to 3.7 volts.
The voltage range depends a lot on cell construction, temperature, load or charge rate, and chemical mix.
For example “lead acid” batteries with lead and sulphuric acid have a cell chemistry voltage of 2.05 volts but their nominal range is 1.8 to 2.4 volts per cell. Translating that to a 6 cell “12 volt” car battery gives you a range of 10.8 to 14.8 volts.
Yeah they had nicad or nimh batteries donated together to create the battery pack. I had an old shaver that was the same way. Laptops with replaceable batteries do the same things
Current power tools still do this, but with 18650 lithium cells, or some larger variant. But now the trendy thing in power tool batteries are the pouch cells, like the kind found in cell phones and slim laptops. I gotta they’re more energy dense, since there’s less of an air gap between cells.
There didn’t used to be efficient ways to convert DC/DC voltages up in electronics (you could drop it, though also not very efficiently), but nowadays there are technologies to do that and hundreds of choices of integrated chips that do most of the work along with a inductor and a diode (these being the very minimal set of parts) with about 90% efficiency, so stuff that needed higher voltages and had to use multi-cell batteries for it in the past, now can be done with batteries that output much lower voltages along with one of these voltage converters (called “boost converters”).
(For those in the know, yeah there was already something before for lower currents called voltage pumps, using only capacitors, but those thongs couldn’t handle higher currents).
Anyways, all this to say that manufacturers can now choose to use smaller and simpler batteries for the equipment they make and convert voltage up in circuitr cheaply and with minimal losses, hence you’re much more likelly to see that when it makes economical sense for them (for example, by being able to use the more common battery types rather that having to have unique custom batteries, as the latter are more expensive since they do not get the same savings from the economies of scale of mass production).
All 9v batteries are just a collection of smaller cells.
Different materials used as basis for different battery techs will produce different voltages when the ions go to the anode (something to do with the energy that can gained when the ions combine with the material of the anode being only one of a fixed set of possibilities due to the available free bands in the atomic structure - please check Wikipedia for a proper and correct explanation rather than my vaguelly remembered one) which is why Lithium batteries are always around 4V without extra electronics to drop the voltage (which make them less efficient) and voltages above that require putting multiple cells in series to add their voltages.
As it so happens, the techs for the Carbon-based, Alkaline and Cadmium all have this voltage be around 1.5V (though you might have noticed that the Cadmium ones are a little lower than 1.5V and Alkaline a little higher) so you need 6x cells in series of batteries of that tech to get 9V.
That I know of, there is no consumer battery tech which has a single cell voltage of 9V and I don’t even know if there is any substance or combinations of substances that makes that possible at all.
Some are also 6x little tiny aaaa batteries
the little round ones are what i remember when i took a 9v apart when i was a kid.
Me too. Like this.
Disapointingly, it came wrapped in a branded metal case that you have to pry apart to see the cool layers.
They used to think that sort of thing was cool in the 90s.
They were right. I stand by this claim.
About a decade ago I told my spouse I wanted to customise my PC with a perspex case and some lighting inside. He was all bleurgh, why would you want to do that?! His current PC has a glass side and rainbow lights inside.
I also stand by this claim and have since the 90s. Thank you and good day, sir.
Better use of space - they used to be just six coin cells with a load of empty space for a wire to connect the top connector to bottom of the stack
